US2862050A - Balanced phase-detection system - Google Patents

Balanced phase-detection system Download PDF

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US2862050A
US2862050A US496141A US49614155A US2862050A US 2862050 A US2862050 A US 2862050A US 496141 A US496141 A US 496141A US 49614155 A US49614155 A US 49614155A US 2862050 A US2862050 A US 2862050A
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signal
phase
signals
circuit
oscillations
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Richman Donald
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Hazeltine Research Inc
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Hazeltine Research Inc
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Priority to US215323D priority Critical patent/USB215323I5/en
Priority to NL114119D priority patent/NL114119C/xx
Priority to NL205635D priority patent/NL205635A/xx
Priority to US496171A priority patent/US3086173A/en
Priority to US496141A priority patent/US2862050A/en
Application filed by Hazeltine Research Inc filed Critical Hazeltine Research Inc
Priority to GB5300/56A priority patent/GB803087A/en
Priority to GB5299/56A priority patent/GB795568A/en
Priority to DEH26580A priority patent/DE1028614B/de
Priority to CH343446D priority patent/CH343446A/de
Priority to FR1148681D priority patent/FR1148681A/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/44—Colour synchronisation
    • H04N9/455—Generation of colour burst signals; Insertion of colour burst signals in colour picture signals or separation of colour burst signals from colour picture signals
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D1/00—Demodulation of amplitude-modulated oscillations
    • H03D1/08—Demodulation of amplitude-modulated oscillations by means of non-linear two-pole elements
    • H03D1/10—Demodulation of amplitude-modulated oscillations by means of non-linear two-pole elements of diodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/64—Circuits for processing colour signals
    • H04N9/70—Circuits for processing colour signals for colour killing

Definitions

  • This invention relates to balanced phase-detection systems and, more particularly, to such systems for utilizing the phase of a reference signal which recurrently occurs for short periods to control the phase of another signal.
  • a reference signal may be the color burst signal employed in an NTSC type of color-television system for controlling the phase of a signal developed in an oscillator of a colortelevision receiver and the invention will be described in such environment.
  • a locally generated signal having difierent phases as applied to different synchronous detectors, is heterodyned in such detectors with a received subcarrier wave signal modulated at specific phases by different color-signal components to derive such components therefrom.
  • the phases of the locally generated signal, as applied to the diflerent synchronous detectors are controlled by means of a received color-synchronizing or burst signal.
  • This phase control may be effected by means of conventional automatic-phase-control circuits or more elaborate circuits having a higher degree of control and stability such as described in an article entitled The D. C.
  • Quadricorrelator A two mode synchronization system at pages 288-299, inclusive, of the January, 1954 Proceedings of the I. R. E.
  • the phase-detector tubes are rendered conductive during the period of occurrence of the burst by amplifying such burst so that the peak intensity thereof is sufficiently high to exceed the cutoff potentials on the detector tubes.
  • a gating circuit is employed prior to the phase detectors for translating the color burst signal for ap plication thereto and for rejecting any other signals occurring between bursts. This type of operation is wasteful of equipment in that it requires a signal-gating stage and greater amplification for the burst signal than would be needed for purely phase-detection purposes.
  • an object of the present invention to provide a new and improved balanced phase-detection system which avoids one or more of the above disad vantages and limitations of prior phase-detection systems.
  • a control system for an NTSC type of colortelevision receiver comprises a chrominance channel including a source of reference oscillations.
  • the control system also comprises means for supplying recurrent color burst signals for synchronizing the oscillations.
  • the system further comprises phase-detection apparatus responsive to the burst signals and the oscillations and including three unidirectional conductive devices and circuit means intercoupling the devices for applying the burst signals and oscillations to the circuit means and devices at such magnitudes and phases as to produce at one point in the circuit means a first control voltage for synchronizing the oscillations and at another point a second control voltage which is an indication of the amplitude of the burst signals when the oscillations are in-synchronism but which is substantially Zero when the oscillations are out-of-synchronism.
  • the system further comprises means for utilizing the first control voltage to synchronize the oscillations.
  • the control system finally comprises means for utilizing the second control voltage to disable the chrominance channel when the oscillations are out-ofsynchronism.
  • Fig. l is a schematic diagram of a color-television receiver including a balanced phase-detection system constructed in accordance with the invention
  • Fig. 2 is a detailed circuit diagram of one embodimen of such phase-detection system
  • Fig. 2a is a vector diagram useful in explaining the operation of the embodiment of Fig. 2;
  • Fig. 3 is a detailed circuit diagram of another embodi ment of such phase-detection system, and.
  • Fig. 3a is a vector diagram uesful in explaining the operation of the embodiment of Fig. 3.
  • a color-television receiver suitable for utilizing an NTSC type of color-television signal.
  • the receiver includes a video-frequency signal source-10 which may be conventional equipment forsupplying an NTSC type of composite video-frequency signal.
  • a video-frequency signal source-10 which may be conventional equipment forsupplying an NTSC type of composite video-frequency signal.
  • it may comprise a radio-frequency amplifier having an input circuit coupled to an antenna 11, an oscillator-modulator, an intermediate-frequency amplifier, and a detection systenmfor deriving the: video-frequency signal.
  • An output cirCUit o the video-frequency signal sourcelOis coupled through a luminance channel including, in cascade, in the order named, a luminance amplifier 12 and a delay line;;13,,to, an input, circuit of.
  • the amplifier 12 may be a conventional wideband amplifier, for example, haying a pass band of approximately 4.2. megacycles and, the delay line 13 may be a. conventional line proportioned to equalize the time of ,translation of theluminancesignal through the amplifier llandgthe. line 1'3 with that for translation of the chrominance signal through achrominance channel to he discussedhereinafter.
  • the color-image-reproducing app aratus 14 may be of ,conventional construction, for" example,; may. comprise a three-gun, cathode-ray tube of the so-caIIedQShadQW-mask type having phosphors for developing three primarycolors' and now employed in many color-television receivers.
  • Such chrominance channel may include, in cascade in the order named, a chroma amplifier 15 and a demodulator and matrix; circuit 16 havingthree output circuits individually coupled to three input circuits of the imagereproducing apparatus 14. Apair of input circuits of the unit;1 6 is coupled' to a pair of output circuits of a 3.58 megacycle' oscillator 17 comprising a source of reference oscillations.
  • the chroma amplifier 15 may be of conventional; construction for translating a component of the video-frequency signal, for example, that portion of the video-frequency signal including the subcarrier Wave signal modulated at specific phases by color-signal components.
  • Such subcarrierwave signal has a mean frequency of. approximately 3.58 megacycles and the side bands thereof usually extend from 2.0 to 4.2 megacycles.
  • the amplifier 15 may have a pass band of the order of 2.0-4.2 megacycles.
  • the color demodulator and matrix circuit 16 may also be of conventional construction including a plurality of synchronous detectors and a signal-matrixing system for developing, for example, colors representative of the green, red, and blue components of a televised image for application to the imagereproducing apparatus 14.
  • the output circuit of the chroma amplifier 15 is also coupledto a balanced phase-detection system 18 constructed in accordance with the present invention and to be described. more fully hereinafter.
  • the detector 18 has another input circuit coupled to an output circuit of the oscillator 17.
  • One output circuit of the unit 18 is coupled through areactance circuit 19 to the 3.58 megacycle oscillator 17 and another output circuit is coupled through a resistor 20 to a gain-control circuit of the chromaamplifierlS and also coupled through a colorkillercircuit 21- and an isolating resistor 22 to the same gain-control circuitof the amplifier 15.
  • Thecolor-killer circuit 2 1 may be. of conventional construction, for example, such as described inthe aforementioned January, 1954 I. R. E. article for developing a large negative bias potential when the oscillator 17 is not synchronized and substantially zero potential when it is synchronized.
  • Another output circuit of the video-frequency signal source-10 is coupled through a synchronizing-signal separator 23 to input circuits of a line-frequency generator 24 and a field-frequency generator 25, the output circuits of the latter units being coupled to horizontal and vertical deflection windings in the color-image-reproducing apparatu's:14;i
  • an output circuit of the generator'24 for example a terminal on the horizontal deflectiontransformer therein, is coupled to input circuits ofthe balanced phase-detection system 18 and of the color-killer circuit 21.
  • a fourth outputcircuit of the video-frequency signal source 10 is coupled to a sound-signal reproducer 26 whlch may-comprise, a conventional intermediate-fre- ,4 quency amplifier, an audio-frequency amplifier, and a sound reproducer such as a loudspeaker.
  • a desired composite color-television signalof the NTSC type is intercepted by the antenna system 11, selected, amplified, converted to an intermediate-frequency signal, further amplified, and the composite video-frequency signal component thereof detected in the unit 10.
  • Such composite video-frequency-signal comprises conventional lineand field-synchronizingcomponents, a color burst synchronizing componentpand luminance and chrominance signals.
  • the chrominance signal is amplified inrthe unit 15 and applied to the demodulator and matrix cirClJitIG.
  • the conventional I'and Q components may be derivedby synchronous detection employing properly phased signals from theoutput circuits of the oscillator'17.
  • the derived I and Q components are then matrixed to RY, B-Y, and G--Y color-difference signals representative, respectively, of the red, blue, and green components of the televised color image.
  • These color-difference signals are'applied to the color-image-reproducing apparatus 14' to combine therein with'the luminance signal to reproduce the televisedimage in color.
  • the balanced phasedetection system 18 compares the phase of a signal developed in the oscillator 17 with: thatoffa color burst synchronizing signal applied to the system 18 froman output circuit of the amplifier 15. Any deviation of the phasing of the signals developed in the oscillator. 17 from a specific phase relation results in the developingof a control signal in an'outputcircuit ofjthe phase-detection system 18.
  • This control signal is employed vby means of the reactance circuitl19 to eliminate such misphasing.
  • a signal developed in the phase-detection systern 18' is also utilizedin' a manner to be describedfmore fully hereinafter to control .the gainof the chroma amplitier 15 thereby. to etfectautomatic gain control for the chrominance and burst signals".
  • An output signal. of the phase-detection system 18' is also employed in the color-killer circuit 21 to develop a bias potential which renders the chroma amplifier 15 nonconductive except when'a burst signal is beingreceived and thefcolor burst and locally generated signals are properly. phased. If these signals are properly phased, the'chroma amplifier is continuousiy conductive.
  • thelineand field-synchronizing signals are separated from the com: posite video-frequency signal and from. each other and are utilized, respectively, in the generators 24 and 25-h) develop horizontal and verticaldeflection signals.
  • the latter signals are. employed in the deflection windings of the apparatus 14 to cause the electron beamof such apparatus to scan a raster on the image screen thereof.
  • a flyback' pulse developed in,f for example, the horizontal deflection transformer in the generator 24 is applied to input circuits of the phase-detection system 18 and colorkiller circuit 21 to cause such units to be operative to develop their diiferent control potentials substantially only during that period when the color burst signal is present.
  • a sound signal is also intercepted and an intermediate-frequency sound signal developed in the source 10.
  • Such intermediate-frequency sound signal is then further amplified in the sound-signal reproducer 26 and the audio-frequency components thereof are detected and additionally amplified and utilized to reproduce sound in the unit 26.
  • phase-detection system 18 of Fig. 1 comprises means for supplying recurrent color burst signals for synchronizing the reference oscillations.
  • supply means comprises a coupling condenser 32, connected between the chroma amplifier 15 and a primary winding of a bifilar transformer 39, for supplying the reference phase of color burst synchronizing signal which occurs during every line-blanking period.
  • the source of reference oscillations comprises a transformer 30 having the primary winding thereof coupled to the oscillator 17 for supplying a controllable phase or locally generated signal.
  • the secondary winding of the transformer 30 is coupled between the interconnected cathodes of a group of diodes 33, 34, and 35 and a reference potential source, for example chassisground, through a pair of series-connected condensers 45 and 46.
  • the condensers 45 and 46 have relatively high impedance for low-frequency signals, for example, for frequencies in the audio-frequency range while having negligible impedance for the color burst or locally gen erated signals having frequencies of the order of 3.58 megacycles.
  • the balanced phase-detection system also includes phasedetection apparatus responsive to the burst signals and the oscillations and including three unidirectional conductive devices and circuit means intercoupling the devices for applying the burst signals and oscillations to the circuit means and devices at such magnitudes and phases as to produce at one point in the circuit means a first control voltage for synchronizing the oscillations and at another point a second control voltage which is an indication of the amplitude of the burst signals when the oscillations are in-synchronism but which is sub stantially zero when the oscillations are out-of-synchronism.
  • such apparatus includes three diodes 33, 34, and 35 having interconnected cathodes to provide effectively one common cathode and each having a load resistor coupled between the anode and cathode, specifically, load resistors 36, 38, and 37.
  • Each diode has a unidirectionally conductive current-carrier path between the cathode and anode thereof, specifically, a path for the flow of electrons.
  • the phase-detection apparatus also includes a phase-modifying network coupling the current-carrier paths for causing the color burst and locally generated signals to have different phaserelaa tions in each of the diodes 33, 34-, and 35.
  • Such network includes the bifilar wound transformer 39 and a phaseshift network comprising a coupling condenser 40 and a circuit 31 broadly resonant at the frequency of the color burst or locally generated signal, specifically, at approximately 3.58 megacycles.
  • the capacitance of the condenser 46 is greater than that of the condenser in the circuit 31 to provide the combination of the condenser 40 and the circuit 31 with the relatively uniform phase-delay characteristics of a delay line and cause the combination to appear substantially as a resistive load to the input circuit'
  • the circuit 31 is coupled through the condenser 40 to the primary winding of the transformer 39. l
  • the ments of a broadly tuned circuit resonant at approximately the frequency of 3.58 megacyclesf The circuit in-.
  • the circuit 31 is connected between the anode of the diode 34 and the reference-potential source, specifically, chassis-ground-
  • the elements of the tuned circuit including the primary of the transformer 39 are proportioned to apply to the anode of the diode 33 a color burst signal of specific phase with relation to the locally generated signal when the oscillator 17 is properly synchronized. This phase is indicated by the vector D in the vector diagram of Fig.
  • the above-described network has a plurality of output circuits in which the first and second control voltages are produced.
  • one of such output circuits includes a condenser 42 coupled between the terminal of the primary winding of the transformer 39 not connected to the anode of the diode33 and a reference potential, for example, ground.
  • Such output circuit produces the second control voltage and is coupled, for example, to a color-killer circuit, such as unit 21 in Fig. 1, and through a resistor 20, shown in Fig. l, to a gain-control circuit of the amplifier 15.
  • Another output circuit produces the first control voltage and includes a condenser 43 coupled between ground and the terminal of the secondary winding of the transformer 39 not connected to the anode of the diode 35.
  • Such other output circuit is effective to develop a conventional automatic-phase-control potential and is coupled for phase-control purposes, for example, to the reactance circuit 19 of Fig. 1.
  • the condensers 42 and 43 have relatively high impedances for signals having frequencies up to half line frequency and negligible impedances for signals having frequencies of the order of 3.58 megacycles.
  • the balanced phase-detection system 18 of Fig. 2 also includes means for supplying a gating signal coincident with the occurrence of the recurrently occurring color burst signal for application to the phase-detection apparatus to render such apparatus responsive to the color burst and locally generated signals only during the dura tion of the gating signal.
  • supply means for the gating signal comprises a conductive path including an isolating resistor 41 coupled between a source of fiyback signal, for example, between a winding on the horizontal deflection transformer in the line-frequency generated 24 and the junction of the condensers 45 and 46.
  • the fiyback signal applied to the interconnected cathodes of the diodes 33, 34, and 35 is negative going to drive such cathodes negative with respect to the anodes of these tubes, thereby rendering the diodes c0nductive during the duration of the flyback. signal.
  • the pair of desired output potentials are obtained by utilizing a'total of only three diodes to provide the functions of a pair of'balanced'phase detectors.
  • the latter improved system is used herein.
  • the color burst signal developed in the primary winding is inductively coupled to the secondary winding for applying a signal having the phase represented by the vector C of Fig. 2a tothe anode of the tube 35.
  • the signal on the primary winding of the transformer 39 is also applied through the condenser 40 to the circuit 31 to develop a signal having the phase represented by the vector B for application to the anode of the diode 34.
  • the vectors CB and DB represent the magnitudes and phases of the composite signals efiectively applied to the diode network as will be explained more fully hereinafter.
  • the negative-going flyback pulses are applied through the resistor 41, the condenser 45, and the secondary winding of the transformer 30 to the cathodes of the diodes 33, 34, and 35 rendering such diodes conductive during the period when the color burst signal is present.
  • the locally generated signal is continuously applied with I the same phase to the cathodes of all of the diodes 33, 34, and 35.
  • the color burst signal is applied to the anodes of these tubes with diiferent phases with respect to the locally generated signal, such as represented by the. vectors B, C, and D of Fig. 2a, when the oscillator 17- 'is.operating in a stable condition, that is, when it is synchronized.
  • Thelow-frequency load circuit for the signals appliedto the diode 34 includes the series circuit of the condensers 45 and 46 while the low-frequency loadcircuits for the signals applied to the diodes 33 and 35 include not only the series circuit of the condensers 45 and 46 but also, respectively, the condensers 42 and 43.
  • the operation of the diodes 33, 34, and 35 to per form both quadrature-phase and in-phase detection may be explained by considering the operation of these diodes in pairs with the diode 34 common to both pairs.
  • the color burst signal applied to the anode of the diode 34 combines with the locally generated signal applied to the cathode thereof, represented by the vector A of Fig. 2a, to develop across the series circuit of the condensers 45 and 46 a unidirectional potential. representative of the phase relation of the applied signals.
  • the signals applied to thediode 35 attempt to develop across the load condenser 43 a potential representative of thephase relation of thevectors-C and, A of Fig. 2a.
  • the potential developed across the condenser 42, when the oscillator 17 the circuits including .the diodes 34 and 35 is, in all respects, a balanced quadrature-phase control potential.
  • This potential is approximately zero when the oscillator 17 is synchronized and the vector relationship represented by the vectors A, B, and C exists and becomes increasingly large and has a characteristic polarity as the oscillator 17 deviates from synchronous operation in either sense.
  • the combined effect of the signals. applied to the diodes 34 and 35 is the equivalent of having a color burst signal, such as represented by the composite vector CB of Fig.
  • the diodes 34 and 35 provide a balanced quadrature-phase detector
  • the diodes 33 and 34 provide a balanced in-phase detector.
  • the signals applied to the diodes 33 and 34 cause average currents to flow therethrough to develop potentials across the condensers 45, 46, and 42.
  • the combined effect of these signals if the signals represented by the vectors B and D are controlled to have the same magnitude, is the equivalent of having a color burst signal, such as represented by the composite vector DB of Fig. 2a for a synchronized condition, applied to these diodes to develop a balanced in-phase potential. Because of the inphase relationship of the locally generated signal, rep resented by the vector A, and the effective signal, represented by the composite vector DB of Fig.
  • the color-killer circuit conditions the chrominance channel to be conductive or nonconductive during picture periods when a color burst signal is, respectively, present or absent.
  • the magnitudes or, more accurately, the variations in the magnitude of the potential developed across the condenser 42 also provide information useful in controlling the gain of the chrominance channel to cause the intensities of the signals developed in the output circuits thereof to be maintained within a relatively narrow range for a much wider range of intensities at the input to such a channel.
  • variations in the potential developed across the condenser 42, when the oscillator 17 is synchronized provide automatic-chrominance-control (ACC) information for the chrominance channel.
  • ACC automatic-chrominance-control
  • the color burst signal in such systems is initially gated to separate it from picture signals and noise and amplified prior to application to the phase detector.
  • Such treatment of the color burst signal not only requires the use of additional gating and amplifying stages in the receiver but also results in the loss of information which could be used to effect automatic chrominance control (ACC).
  • ACC automatic chrominance control
  • a synchronously detected ACC control potential of the type just described provides many benefits not available in prior ACC systems employing simple peak detection. Since synchronous detection is employed, the developed ACC control potential is relatively free from noise and thus more accurately controls the gain of the chrominance channel. Such gain is controlled substantially only in relation to the amplitude of the burst signal and is little disturbed by noise.
  • an ACC potential of the type developed in a system such as the detection system 18 of Fig. 2 provides maximum gain of the chrominance channel when the local oscillator is not synchronized and, consequently, provides a color burst signal of maximum amplitude at such time resulting 1 10 in the obtaining of more rapid synchronization.
  • such ACC system provides a color burst signal of minimum and constant amplitude substantially free of all noise when the system is synchronized, at which time the maximum ACC potential is being developed.
  • Resistor 41 1000 ohms.
  • the improved phase-detection system 18- of Fig. 2 is a complete balanced phase-detection system providing both in-phase and quadrature-phase detection though only three diodes are employedinstead of the conventional four-diode arrangement.
  • the detection system 18 of Fig. 2 utilizes a third signal to elfect gating of the detectors and further utilizes a color burst signal of relatively low amplitude thereby facilitating the development of an ACC potential for controlling the gain of the chrominance channel.
  • the gating of the detection system dispenses with the need for preliminary gating of the burst signal and the use of a relatively low amplitude burst signal minimizes the number of stages of amplification required for the burst signal.
  • the phases of the color burst signal applied to the anodes of the tubes 33, 34, and 35 are represented, respectively, by the vectors D, B, and C of Fig. 3a.
  • the phase of the locally generated signal applied to the cathodes of the diodes 33, 34, and 35 is represented by the vector A of Fig. 3a.
  • the diodes 34 and 35 in the system 318 of Fig. 3 operate as a pair of balanced phase detectors to develop the APC control potential across the condenser 43.
  • the diodes 33 and 35 operate as another pair of balanced phase detectors to develop across the condenser 42 a signal which has an in-phase component.
  • the balanced phase-detection system described-herein have utilizedrthree diodesfwith interconnected .cathodes--and--separate anodesfit is -to 'be understcod that, in-accordance with 'the invention, the anodes may be interconnected and the cathodes separate, and vacuum tubes other than diodes may be employed.
  • the detection systems have been described with reference to vacuum tubes, other nonlinear elements, such as transistors or crystal diodes, performing functions similar to. those of vacuum tubes maybe employed in accordance with, thegteaching of the invention.
  • the networks described for effecting the phase adjusting of the signals applied to the diodes maytake any of numerous conventional forms in addition ;to. those described herein.
  • a balancedphase-detection system for the colorsignal deriving circuits of an NTSC type of colortelevision receiver comprising: means for supplying a locally generated. signal of controllable phase and a recurrent .color burst synchronizing signal of variable intensity lower than that of said locally generated signal for controlling the phase of said locally generated signal; phase-detection apparatusincluding three diodes effectively, having one cathode responsive to one of said signals and three anodes, a plurality of reactively coupled impedance circuits individually coupled to said anodes for applying the other one of said'signals thereto with different phases, and a pair of balanced output circuits coupled to said impedance circuits for developing one balanced output potential representative of the quadrature-phase relationship of said supplied signals and for developing another balanced output potential representative of the in-phase relationship of said supplied signals and which varies in intensity with said variation in the intensity of said color burst signal; a line-frequency deflection circuit for supplying a negative horizontal fiyback pulse coincident with saiducolor
  • burst synchronizing signal 12 for application to said cathpde to render said phase; detection apparatu'sresponsive" to said supplled signals onlyduring the durationbf said flybacli pul's'efand for utilizi'ng'said intensity variation of said other balanced outputsignal to minimize the intensity variation of said color burst synchronizing signal.
  • a control system for an NTSC type of colortelevision receiver comprising: a chrominance channel including a source ofreference oscillations; means for supplying recurrent color burst signals forsynchronizing said oscillations; phase-detection apparatus responsive to said burst signals and said oscillations and including three unidirectionalconductive devices and circuit means'intercoupling said devices for applying saidburst signals and oscillations to said circuit means and devices at such magnitudes and phases as to produce at one point in said circuit means a first control voltage for synchronizing said oscillations and at another point a second control voltage which is an indication-of the amplitude of said burst signals when said oscillations are in-synchronism but which is'substantially zero when said oscillations are out-of-synchronism; means for utilizing said first control'voltage to synchronize said oscillations; and means for utilizing said second control voltage'to disablesaid chrominance channel when said magnitudes and phases as to produce at one point in' said circuit means a first control
  • a control system for an NTSC type of colortelevision receiver comprising: a chrominance channel including a source of reference oscillations; means for supplying recurrent color burst signals for synchronizing said oscillations; phase-detection apparatus responsive to said burst signals and saidoscillations and including'three unidirectional conductive devices and circuit meansintercoupling said devices for applying said burst signals and oscillations to said circuit means and devices at such magnitudes and phases as to produce at one point in said circuit means a first control voltagefor synchronizing said oscillations and at another point a second control voltage which'is an indication of the amplitude of .said burst signals when said oscillations are in-synchronism but which is substantially zero when said oscillations are out-of-synchronism; means for utilizing said first control aeeaoso and oscillations to said circuit means and devices at such magnitudes and phases as to produce at one point in said circuit means a first control voltage for synchronizing said oscillations and at
  • a control system for an NTSC type of colortelevision receiver comprising: a chrominance channel including a source of reference oscillations; means for supplying recurrent color burst signals for synchronizing said oscillations; phase-detection apparatus responsive to said burst signals and said oscillations and including three unidirectional conductive devices and circuit means intercoupling said devices for applying said burst signals and oscillations to said circuit means and devices at such magnitudes and phases as to produce at one point in said circuit means a first control voltage for synchronizing said oscillations and at another point a second control voltage which is an indication of the amplitude of said burst signals when said oscillations are in-synchronism but which is substantially zero when said oscillations are out of synchronism; means for supplying a gating signal coincident with the occurrence of said burst signals for rendering said phase-detection apparatus so responsive only during the duration of said gating signal; means for utilizing said first control voltage to syn chronize said oscillations

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Power Engineering (AREA)
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US496141A 1955-03-23 1955-03-23 Balanced phase-detection system Expired - Lifetime US2862050A (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title
NL205635D NL205635A (enrdf_load_html_response) 1955-03-23
US215323D USB215323I5 (enrdf_load_html_response) 1955-03-23
NL114119D NL114119C (enrdf_load_html_response) 1955-03-23
US496141A US2862050A (en) 1955-03-23 1955-03-23 Balanced phase-detection system
US496171A US3086173A (en) 1955-03-23 1955-03-23 Balanced phase-detection system
GB5300/56A GB803087A (en) 1955-03-23 1956-02-21 Balanced phase-detection system
GB5299/56A GB795568A (en) 1955-03-23 1956-02-21 Balanced phase-detection system
DEH26580A DE1028614B (de) 1955-03-23 1956-03-19 Einrichtung, insbesondere fuer Fernsehempfaenger, zur Erzeugung zweier Steuerspannungen, welche vom gegenseitigen Phasenverhaeltnis zweier der Einrichtung zugefuehrten Spannungen annaehernd gleicher Frequenz in verschiedener Weise abhaengig sind
CH343446D CH343446A (de) 1955-03-23 1956-03-19 Einrichtung, insbesondere für Fernsehempfänger, zur Erzeugung zweier Steuerspannungen, welche vom gegenseitigen Phasenverhältnis zweier der Einrichtung zugeführten Spannungen annähernd gleicher Frequenz in verschiedener Weise abhängig sind
FR1148681D FR1148681A (fr) 1955-03-23 1956-03-23 Récepteur de télévision

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US496141A US2862050A (en) 1955-03-23 1955-03-23 Balanced phase-detection system

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US2862050A true US2862050A (en) 1958-11-25

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US496141A Expired - Lifetime US2862050A (en) 1955-03-23 1955-03-23 Balanced phase-detection system

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US215323D Pending USB215323I5 (enrdf_load_html_response) 1955-03-23

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US (2) US2862050A (enrdf_load_html_response)
CH (1) CH343446A (enrdf_load_html_response)
DE (1) DE1028614B (enrdf_load_html_response)
FR (1) FR1148681A (enrdf_load_html_response)
GB (2) GB795568A (enrdf_load_html_response)
NL (2) NL114119C (enrdf_load_html_response)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL297671A (enrdf_load_html_response) * 1962-11-29
US3291902A (en) * 1963-10-17 1966-12-13 Gen Electric Synchronous detector

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2568250A (en) * 1947-04-01 1951-09-18 Decca Record Co Ltd Phase comparator circuits
US2640939A (en) * 1950-02-11 1953-06-02 Int Standard Electric Corp Phase detector
US2666136A (en) * 1950-10-31 1954-01-12 Rca Corp Frequency synchronizing apparatus
US2703380A (en) * 1949-09-21 1955-03-01 Sperry Corp Phase comparison apparatus for data transmission systems
US2718546A (en) * 1952-11-26 1955-09-20 Motorola Inc Phase detector

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2568250A (en) * 1947-04-01 1951-09-18 Decca Record Co Ltd Phase comparator circuits
US2703380A (en) * 1949-09-21 1955-03-01 Sperry Corp Phase comparison apparatus for data transmission systems
US2640939A (en) * 1950-02-11 1953-06-02 Int Standard Electric Corp Phase detector
US2666136A (en) * 1950-10-31 1954-01-12 Rca Corp Frequency synchronizing apparatus
US2718546A (en) * 1952-11-26 1955-09-20 Motorola Inc Phase detector

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NL114119C (enrdf_load_html_response)
DE1028614B (de) 1958-04-24
GB803087A (en) 1958-10-15
FR1148681A (fr) 1957-12-12
GB795568A (en) 1958-05-28
CH343446A (de) 1959-12-31
NL205635A (enrdf_load_html_response)
USB215323I5 (enrdf_load_html_response)

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